Bioherbicidal effects of essential oils of Nepeta meyeri Benth. on weed spp.

The chemical composition of essential oils isolated by hydrodistillation from the aerial parts of Nepeta meyeri was analyzed by GC-MS. Fourteen compounds were identified in the essential oil of N. meyeri, representing more than 99.07% of oil, of which the major components were: 4a alpha,7 alpha,7a beta-nepetalactone (83.4%), 4a alpha,7 alpha,7a alpha-nepetalactone (8.83%), (Z)-sabinene hydrate acetate (3.26%) and germacrene D (0.98%). The oils had relatively high content of oxygenated monoterpenes. The bioactivity of essential oils was tested against 10 weed species (Amaranthus retroflexus L., Portulaca olerace L., Bromus danthoniae Trin., Agropyron cristatum L., Lactuca serriola L., Bromus tectorum L., Bromus intermedius Cuss., Chenopodium album L., Cynodon dactylon L., Convolvulus arvensis L.). The N. meyeri essential oils inhibited the seed germination and seedling growth of all test weed spp. The herbicidal activity of the oils can be attributed to their relatively high content of oxygenated monoterpenes, especially 4a alpha,7 alpha,7a beta-nepetalactone. These findings suggest that the essential oils of N. meyeri have the potential for herbicide.